Browsing by Author "Gidley, MJ"
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- ItemDifferential effects of genetically distinct mechanisms of elevating amylose on barley starch characteristics(Elsevier Science Ltd, 2012-07-01) Regina, A; Blazek, J; Gilbert, EP; Flanagan, BM; Gidley, MJ; Cavanagh, C; Ral, JP; Larroque, O; Bird, AR; Li, ZY; Morell, MKThe relationships between starch structure and functionality are important in underpinning the industrial and nutritional utilisation of starches. In this work, the relationships between the biosynthesis, structure, molecular organisation and functionality have been examined using a series of defined genotypes in barley with low (<20%), standard (20–30%), elevated (30–50%) and high (>50%) amylose starches. A range of techniques have been employed to determine starch physical features, higher order structure and functionality. The two genetic mechanisms for generating high amylose contents (down-regulation of branching enzymes and starch synthases, respectively) yielded starches with very different amylopectin structures but similar gelatinisation and viscosity properties driven by reduced granular order and increased amylose content. Principal components analysis (PCA) was used to elucidate the relationships between genotypes and starch molecular structure and functionality. Parameters associated with granule order (PC1) accounted for a large percentage of the variance (57%) and were closely related to amylose content. Parameters associated with amylopectin fine structure accounted for 18% of the variance but were less closely aligned to functionality parameters. © 2012, Elsevier Ltd.
- ItemEffects of processing high amylose maize starches under controlled conditions on structural organisation and amylase digestibility(Elsevier, 2009-01-22) Htoon, AK; Shrestha, AK; Flanagan, BM; Lopez-Rubio, A; Bird, AR; Gilbert, EP; Gidley, MJThe amylase digestibility of high-amylose maize starches has been compared before and after thermo-mechanical processing. Starches were analysed for enzyme-resistant starch yield, apparent amylose content, crystallinity (X-ray diffraction), and molecular order (NMR and FTIR), both before and after treatment with (x-amylase. All samples had significant (>10%) enzyme-resistant starch levels irrespective of the type and extent of thermal or enzymic processing. Molecular or crystalline order was not a pre-requisite for enzyme resistance. Near-amorphous forms of high amylose maize starches are likely to undergo recrystallisation during the enzyme-digestion process. The mechanism of enzyme resistance of granular high-amylose starches is found to be qualitatively different to that for processed high-amylose starches. For all samples, measured levels of enzyme resistance are due to the interruption of a slow digestion process, rather than the presence of completely indigestible material. © 2008, Elsevier Ltd.
- ItemEffects of thermal denaturation on the solid-state structure and molecular mobility of glycinin(American Chemical Society, 2011-06-01) Huson, MG; Strounina, EV; Kealley, CS; Rout, MK; Church, JS; Appelqvist, IAM; Gidley, MJ; Gilbert, EPThe effects of moisture and thermal denaturation on the solid-state structure and molecular mobility of soy glycinin powder were investigated using multiple techniques that probe over a range of length and time scales. In native glycinin, increased moisture resulted in a decrease in both the glass transition temperature and the denaturation temperature. The sensitivity of the glass transition temperature to moisture is shown to follow the Gordon-Taylor equation, while the sensitivity of the denaturation temperature to moisture is modeled using Flory's melting point depression theory. While denaturation resulted in a loss of long-range order, the principal conformational structures as detected by infrared are maintained. The temperature range over which the glass to rubber transition occurred was extended on the high temperature side, leading to an increase in the midpoint glass transition temperature and suggesting that the amorphous regions of the newly disordered protein are less mobile. C-13 NMR results supported this hypothesis. © 2011, American Chemical Society
- ItemEnzyme resistance and structural organization in extruded high amylose maize starch(Elsevier, 2010-05-05) Shrestha, AK; Ng, CS; Lopez-Rubio, A; Blazek, J; Gilbert, EP; Gidley, MJGelose 80, a high amylose maize starch, was extruded in a twin screw extruder at different feed moistures, cooled, stored for 12 days at 4°C, and cryo-milled. The raw and extruded starches were analysed for in vitro enzyme-resistant starch content (ERS), morphology, in vitro digestibility, long range (X-ray diffraction) and short range (FTIR) molecular order. Extrusion markedly increased the rate of starch digestion and reduced the ERS content, irrespective of whether B-type or B- and V-type polymorphs were present. Increasing feed moisture and storage resulted in only slight increases in ERS content, with X-ray diffraction and FTIR also showing small changes in long and short range molecular order, respectively. Analysis of residues from in vitro digestion showed the mechanism of enzyme resistance of granular and extruded high amylose starch to be markedly different, both qualitatively and quantitatively. Enzyme digestion of granular high amylose maize starch showed initial disorganization in structure followed by slow reorganization at later stages of digestion. In contrast, molecular reorganization took place throughout the enzyme digestion of extruded high amylose maize starch. Higher levels of crystallinity were found in digested extrudates compared with digested granules, showing that there is no direct correlation between starch crystallinity and enzyme digestion rates. © 2009, Elsevier Ltd.
- ItemHierarchical architecture of cellulose and its interaction with other plant cell wall polysaccharides(Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-18) Martínez-Sanz, M; Lopez-Sanchez, P; Mikkelsen, D; Flanagan, BM; Gidley, MJ; de Campo, L; Rehm, C; Gilbert, EPPlant cell walls (PCWs) are extremely complex structures in which cellulose microfibrils are hier archically assembled and embedded in a multi-component matrix. While the cellulose microfibrils represent the basic building unit providing mechanical strength [1], the matrix components are able to tune the properties of each specific tissue [2-3], increasing the flexibility or limiting the transport of moisture, for instance. The synthesis of cellulose hydrogels by means of bacterial fermentation is an efficient approach to mimic the cell wall biosynthesis process and investigate the interactions established between cellu lose and matrix polysaccharides by incorporating the latter into the culture medium. We have char acterised cellulose hydrogels and their composites with PCW polysaccharides by means of SANS and SAXS, combined with complementary techniques such as X-ray diffraction, spectroscopy and microscopy. Furthermore, the production of partially deuterated cellulose hydrogels by using a deuterated glucose-based feedstock is presented as a strategy to enhance the neutron scattering length density contrast [4]. The application of a multi-technique characterisation approach enabled elucidation of the complex hierarchical architecture of cellulose hydrogels and led to the development of a multi-scale model based on core-shell structures [4-8]. The model describes the multi-phase structure of cellulose microfibrils and ribbons, as well as the essential role of water at the different structural levels. In addition, USANS experiments are presented as a promising method to characterise the structure of native cellulose in the longitudinal direction, providing information on the microfibril length and ribbon twisting periodicity. PCW polysaccharides such as xyloglucan, arabinoxylan, mixed linkage glucans and pectins during cellulose synthesis have a distinct structural role and interaction mechanism with cellulose (interfering with the crystallisation process and strongly interacting with the cellulose microfibrils, or establishing interactions at the ribbons’ surface level). These results highlight the ability of small angle scattering techniques to provide valuable insights on cellulose biosynthesis and interactions with PCW polysaccharides. © The Authors.
- ItemHydration induced structural changes in native, denatured and protected soy glycinin (11s)(Institute of Food Technologists, 2007-07) Appelqvist, IAM; Rout, MK; Chanvrier, H; Dezfouli, M; Kelly, M; Htoon, AK; Kealley, CS; Gilbert, EP; Strounina, E; Whittaker, AK; Gidley, MJ; Lillford, PJProteins and other biomolecules undergo a dynamic transition to a glass-like solid state with small atomic fluctuations. This dynamic transition can inhibit biological function and alter their material properties.
- ItemHydration study of soy protein in the ‘dry state’(Royal Society of Chemistry, 2008-05-19) Kealley, CS; Rout, MK; Appelqvist, IAM; Strounina, EV; Whittaker, AK; Gidley, MJ; Gilbert, EP; Lillford, PJThe work reported focuses on the methodology employed by the Australian Food Futures collaboration to the study of proteins in the dry state. To date, 'dry' proteins (here used to describe solids with a moisture content <30% w/w) have been characterised by differential scanning calorimetry (DSC), fourier transform - infrared spectroscopy (FT-IR), 1H t2 relaxation and 13C high resolution nuclear magnetic resonance (NMR) spectroscopy and small angle x-ray scattering (SAXS). The case study presented in this paper centres on the use of these techniques to characterise the differences in structure between native and denatured glycinin, a soy protein, at low and controlled moisture contents. The glass transition temperature of native soy glycinin (11S) at room temperature (∼ 27°C), is at a moisture content of 13.4%, whereas the denatured soy glycinin undergoes a glass transition at 46°C at the same moisture content. With increasing water content, NMR experiments show that proton exchange with protein surfaces (*H T2) and protein segmental mobility (13C) both increase. A β - sheet toβ - turn structural rearrangement is inferred as the position of the Amide-I FT-IR band shifts from 1634 to 1630 cm"1. Proton T2 relaxation rates range from < 1 ms to 25 ms, with shorter (< 1 ms) relaxation rates dominant up to 17.4% moisture for both native and denatured glycinin. ,13C NMR experiments show motional heterogeneity for native glycinin, with a more uniform and restricted mobility after denaturation. Small angle scattering data show an expansion of -7% in the unit cell of the material as the moisture content is increased from 4.6% up to 13.4%, however there are no significant crystalline or other major structural changes in the protein over the spatial dimension probed (1-100 nm). © The Royal Society of Chemistry 2008.
- ItemInfluence of storage conditions on the structure, thermal behavior, and formation of enzyme-resistant starch in extruded starches(American Chemical Society, 2007-10-26) Chanvrier, H; Uthayakumaran, S; Appelqvist, IAM; Gidley, MJ; Gilbert, EP; Lopez-Rubio, AStarch structures from an extrusion process were stored at different temperatures to allow for molecular rearrangement (retrogradation); their thermal characteristics (DSC) and resistance to amylase digestion were measured and compared. The structure of four native and processed starches containing different amylose/amylopectin compositions (3.5, 30.8, 32, and 80% amylose content, respectively) before and after digestion was studied with small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD). Rearrangement of the amylose molecules was observed for each storage condition as measured by the DSC endotherm at around 145°C. The crystalline organization of the starches after processing and storage was qualitatively different to that of the native starches. However, there was no direct correlation between the initial crystallinity and the amount of enzyme-resistant starch (ERS) measured after in vitro digestion, and only in the case of high-amylose starch did the postprocess conditioning used lead to a small increase in the amount of starch remaining after the enzymatic treatment. From the results obtained, it can be concluded that retrograded amylose is not directly correlated with ERS and alternative mechanisms must be responsible for ERS formation. © 2007, American Chemical Society
- ItemMolecular interactions of a model bile salt and porcine bile with (1,3:1,4)-β-glucans and arabinoxylans probed by 13C NMR and SAXS(Elsevier, 2016-04-15) Gunness, P; Flanagan, BM; Mata, JP; Gilbert, EP; Gidley, MJTwo main classes of interaction between soluble dietary fibres (SDFs), such as (1,3:1,4)-β-d-glucan (βG) and arabinoxylan (AX) and bile salt (BS) or diluted porcine bile, were identified by 13C NMR and small angle X-ray scattering (SAXS). Small chemical shift differences of BS NMR resonances were consistent with effective local concentration or dilution of BS micelles mostly by βG, suggesting dynamic interactions; whilst the reduced line widths/intensities observed were mostly caused by wheat AX and the highest molecular size and concentrations of βG. SAXS showed evidence of changes in βG but not AX in the presence of BS micelles, at >13 nm length scale consistent with molecular level interactions. Thus intermolecular interactions between SDF and BS depend on both SDF source and its molecular weight and may occur alone or in combination. © 2015 Elsevier Ltd
- ItemMolecular rearrangement of starch during in vitro digestion: toward a better understanding of enzyme resistant starch formation in processed starches(American Chemical Society, 2008-07) Lopez-Rubio, A; Flanagan, BM; Shrestha, AK; Gidley, MJ; Gilbert, EPResistant starch (RS) is defined as the fraction of starch that escapes digestion in the small intestine, serving as a fermentation substrate for beneficial colonic bacteria. Several studies have been focused on the description of the RS fractions from different starch varieties, but little attention has been paid to the digestion process itself that, from the present work, seems to play a key role in the generation of enzyme-RS (ERS), as determined in vitro. High-amylose starch samples, extruded at two different processing conditions, have been characterized at different stages of in vitro digestion using scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), infrared spectroscopy (FF-IR), solid state C-13 NMR spectroscopy, and X-ray diffraction (XRD). Control samples kept for 18 h in the digestion solution without starch hydrolyzing enzymes (alpha-amylase and amyloglucosidase) were used for comparison purposes. An increase in molecular order was favored by the hydrolytic action of the enzymes, reflected in an increase in double helical order observed by NMR, higher crystallinity measured by XRD, and corresponding changes in FT-IR spectra. An increase in the intensity of the scattering objects was also observed by SAXS as a function of digestion. SAXS from the dry ERS fractions reveals the 001 reflection of crystallites formed during the digestion process, corresponding to a characteristic dimension of the resistant crystalline fraction of similar to 5 nm. The changes found suggest that enzyme resistant starch does not refer to a specific structure present in predigested starches, but may in fact be formed during the digestion process through the rearrangement of amylose chains into enzyme-resistant structures of higher crystallinity. Therefore, the resistance to enzyme digestion of a specific processed starch is the result of a competition between the kinetics of enzyme hydrolysis and the kinetics of amylose retrogradation. © 2008, American Chemical Society
- ItemMolecular, mesoscopic and microscopic structure evolution during amylase digestion of maize starch granules(Elsevier Science Ltd, 2012-09-01) Shrestha, AK; Blazek, J; Flanagan, BM; Dhital, S; Larroque, O; Morell, MK; Gilbert, EP; Gidley, MJCereal starch granules with high (>50%) amylose content are a promising source of nutritionally desirable resistant starch, i.e. starch that escapes digestion in the small intestine, but the structural features responsible are not fully understood. We report the effects of partial enzyme digestion of maize starch granules on amylopectin branch length profiles, double and single helix contents, gelatinisation properties, crystallinity and lamellar periodicity. Comparing results for three maize starches (27, 57, and 84% amylose) that differ in both structural features and amylase-sensitivity allows conclusions to be drawn concerning the rate-determining features operating under the digestion conditions used. All starches are found to be digested by a side-by-side mechanism in which there is no major preference during enzyme attack for amylopectin branch lengths, helix form, crystallinity or lamellar organisation. We conclude that the major factor controlling enzyme susceptibility is granule architecture, with shorter length scales not playing a major role as inferred from the largely invariant nature of numerous structural measures during the digestion process (XRD, NMR, SAXS, DSC, FACE). Results are consistent with digestion rates being controlled by restricted diffusion of enzymes within densely packed granular structures, with an effective surface area for enzyme attack determined by external dimensions (57 or 84% amylose - relatively slow) or internal channels and pores (27% amylose - relatively fast). Although the process of granule digestion is to a first approximation non-discriminatory with respect to structure at molecular and mesoscopic length scales, secondary effects noted include (i) partial crystallisation of V-type helices during digestion of 27% amylose starch, (ii) preferential hydrolysis of long amylopectin branches during the early stage hydrolysis of 27% and 57% but not 84% amylose starches, linked with disruption of lamellar repeating structure and (iii) partial B-type recrystallisation after prolonged enzyme incubation for 57% and 84% amylose starches but not 27% amylose starch. © 2012, Elsevier Ltd.
- ItemThe multi-scale architecture of cellulose hydrogels investigated by small angle scattering techniques(International Conference on Neutron Scattering, 2017-07-12) Martinez-Sanz, M; Gidley, MJ; Gilbert, EPRegardless of its source, native cellulose is characterised by a complex architecture composed of distinct structural features (i.e.cellulose nanocrystals, microfibrils and bundles or ribbons) which are hierarchically arranged. Although deconstruction methods based on sequential component extraction and/or hydrolytic treatments have been typically used to study the structure of cellulose in plant-based resources, they are of limited relevance due to the intrinsic structural alterations induced by these treatments. An alternative approach is the synthesis of highly pure cellulose hydrogels by means of bacterial fermentation. Small angle neutron and X-ray scattering (SANS and SAXS) techniques are an extremely powerful tool to characterise the native structure of highly hydrated cellulose hydrogels, covering the whole size range of interest and, unlike most characterisation methods, avoiding sample drying processes which affect the native cellulose structure. This work demonstrates the potential of a multi-technique approach based on the combination of SANS and SAXS with X-ray diffraction, spectroscopy and microscopy to elucidate the hierarchical structure of cellulose hydrogels. A multi-scale model based on core-shell cylindrical structures has been built and applied to the scattering data. This has revealed the multi-phase structure of the cellulose microfibrils and ribbons, as well as the essential role of water at the different structural levels. In addition, ultra-small angle neutron scattering (USANS) experiments are presented as a promising method to characterise the structure of cellulose in the longitudinal direction, providing information on the microfibril length and ribbon twisting periodicity.
- ItemNovel approach for calculating starch crystallinity and its correlation with double helix content: a combined XRD and NMR study(Wiley-Blackwell, 2008-09) Lopez-Rubio, A; Flanagan, BM; Gilbert, EP; Gidley, MJA peak fitting procedure has been implemented for calculating crystallinity in granular starches. This methodology, widely used for synthetic polymers, is proposed to better reflect the crystalline content of starches than the method normally used, in which it is assumed that relatively perfect crystalline domains are interspersed with amorphous regions. The new approach takes into account irregularities in crystals that are expected to exist in semicrystalline materials. Therefore, instead of assuming that the amorphous background extends up to the base of diffraction peaks, the whole X-ray diffraction (XRD) profile is fitted to an amorphous halo and several discrete crystalline diffraction peaks. The crystallinity values obtained from the XRD patterns of a wide range of native starches using this fitting technique are very similar to the double helix contents as measured by C-13 solid state NMR, suggesting that double helices in granular starches are present within irregular crystals. This contrasts with previous descriptions of crystalline and noncrystalline double helices that were based on the analysis of XRD profiles as perfect crystals interspersed in a noncrystalline background. Furthermore, with this fitting methodology it is possible to calculate the contribution from the different crystal polymorphs of starch to the total crystallinity. © 2008, Wiley-Blackwell.
- ItemStructure and molecular mobility of soy glycinin in the solid state(American Chemical Society, 2008-10) Kealley, CS; Rout, MK; Dezfouli, MR; Strounina, E; Whittaker, AK; Appelqvist, IAM; Lillford, PJ; Gilbert, EP; Gidley, MJWe report a multitechnique study of structural organization and molecular mobility for soy glycinin at a low moisture content (<30% w/w) and relate these to its glass-to-rubber transition. Small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy are used to probe structure and mobility on different length and time scales. NMR (similar to 10(-6) to 10(-3) s) reveals transitions at a higher moisture content (> 17%) than DSC or SAXS, which sample for much longer times (similar to 10 to 10(3) s) and where changes are detected at > 13% water content at 20 degrees C. The mobility transitions are accompanied by small changes in unit-cell parameters and IR band intensities and are associated with the enhanced motion of the polypeptide backbone. This study shows how characteristic features of the ordered regions of the protein (probed by SAXS and FTIR) and mobile segments (probed by NMR and DSC) can be separately monitored and integrated within a mobility transformation framework. © 2008, American Chemical Society